The optical fiber is composed of a circular-in-section core serving as an optical path, and a tubular clad surrounding the core, and its outer periphery is sheathed as required. In an optical transmission system using such optical fibers as a means for information and/or energy transmission, there are provided optical switches for switching the optical path, and optical connectors for connecting or extending the optical path. For the interconnection of two optical fibers at the optical switches or optical connectors, it is important to make the optical axis of one optical fiber coincident with the optical axis of the other optical fiber in order to maintain the optical path at good transmission characteristics, because the core that forms the optical path of the optical fiber has an extremely thin diameter.
Optical switches (switches for switching the transmission path) are commonly considered indispensable for transmission systems using optical fibers, and there have been proposed various types of optical switches. Among others, movable-fiber type optical switches that allow the optical fibers to be directly moved and switched are regarded promising by virtue of their high switching speed, low control voltage, frequency independence of characteristics, as well as low price and good miniaturizability. Further, for such movable-fiber type optical switches, there has been a demand for the realization of those capable of functioning as a two-input, two-output optical switch.
A conventionally known movable-fiber type optical switch that has realized such two-inputs and two-outputs is disclosed in Japanese Patent Laid-Open Publication No. SHO 61-272713. The construction of this prior-art optical switch is explained with reference to FIG. 73. In a casing 302 of an optical switch 301, a pair of blocks 303, 304 are disposed. The first block 303 is fixed to the casing 302 by a leg portion 305. The first and second blocks 303, 304 have through holes 306, 307 (which otherwise may be recesses), respectively, as well as side faces 308, 309 slanted at a specified angle with respect to the center axes of the through holes 306, 307. Further, a pair of plate springs 310 are fixed by screws 311 to the side faces 308, 309 of the first and second blocks 303, 304. Thus, the second block 304 is supported on the first block 303 with the plate springs 310. On both sides of the second block 304 are disposed stoppers 312, respectively. Further, on one side of the second block 304, there is disposed, for example, an electromagnetic actuator 313, which is capable of driving the second block 304 in a direction of arrow 314 against the elasticity of the plate spring 310.
Into the through holes 306, 307 of the first and second blocks 303, 304 of the optical switch 301 as described above, are inserted pin holders 317 and 318 holding three optical fibers 315a, 315b, 315c and 316a, 316b, 316c, respectively, where the pin holders 317, 318 are held so that the end faces of the pin holders 317, 318 come into in contact with each other. In these pin holders 317, 318, each three optical fibers 315a, 315b, 315c and 316a, 316b, 316c extend up to the end faces of the pin holders 317, 318, and are arranged precisely at a specified pitch at the end faces, with the end faces of the optical fibers 315a, 315b, 315c and 316a, 316b, 316c being exposed to the end faces of the pin holders 317, 318. Further, although not shown, the other end of the optical fiber 315c and the other end of the optical fiber 316a are connected to each other via an optical attenuator (not shown).
Thus, when the plate springs 310 are in a generally straight, normal state without any external force acting on the first and second blocks 303, 304, the optical fibers 315a and 316a are in an optical transmission relation, the optical fibers 315b and 316b are in an optical transmission relation, and the optical fibers 315c and 316c are in an optical transmission relation, as schematically shown in FIG. 74A. Accordingly, in this state, the optical fibers 315a and 316c have an optical transmission relation with each other via the optical fibers 316a and 315c.
On the other hand, when the actuator 313 is driven so that an external force along the arrow 314 acts on the second block 304, the plate spring 310 is elastically deformed, causing the second block 304 to be laterally displaced along the arrow 314. As a result, as shown in FIG. 74B, the optical fibers 315a and 316b are positioned in a line so as to come into an optical transmission relation, while the optical fibers 315b and 316c are also positioned in a line. Thus, an inversion switching of the optical switch 301 is effected.
However, such conventional optical switches would involve complex construction of the optical fiber array because each optical fiber array is made up by inserting three optical fibers into a pin holder, and inserting this pin holder into the through hole or recess of the first or second block. This would result in large size of the optical fiber array as well as heavy weight. Further, because of also increased size of optical switches as well as heavy weight of optical fiber arrays, it would be difficult to attain faster switching speeds.
Also, the optical fiber array would be required to have an extremely high precision for the array pitch of the optical fibers. For example, connecting two optical fibers of the graded index type with core diameter 50 .mu.m and clad diameter 125 .mu.m oppositely to each other would involve a tolerance of 3 .mu.m or less, an extremely high precision. As a result, extremely high level of machining would be required for the first or second block with a through hole or recess provided, which in turn would need high molding precision also for the pin holders. This would make a factor of increase in the cost of the optical fiber array, as a disadvantage.
Even if the dimensional precision or the like for the first or second block can be obtained, it would be difficult to attain as high precision of adjustment as, for example, a tolerance of 3 .mu.m because the standstill position of the movable-side block is restricted by adjusting the amount of projection of the stopper. As a result, it has been difficult to attain the positioning of the optical fiber array, and in turn to obtain the precision of optical axis alignment of the optical fibers.
Also, since it needs a large force to displace the second block by overcoming the inertia due to the mass of the block or the reaction force of the plate spring, the actuator for driving the second block would be large sized. As a result, the optical switch itself would be large sized, the power consumption would also be increased, and the manufacturing cost of the actuator would be increased, as further problems. Further, due to the large inertia of the second block and the reaction force of the plate spring, it would be difficult to attain faster switching speed of the switching operation.
Furthermore, since the optical fibers would make contact with jigs or the like in the assembling process of the optical fibers, foreign matters would stick to the end faces of the end portions of the optical fibers. This would cause the optical transmission characteristics to be deteriorated.
Generally, the optical fiber is formed from glass or plastics, and extremely thin diameters are employed to obtain good optical transmission characteristics. Therefore, the optical fiber would be so weak in strength and inadequate to forcedly bend. As a result, there has been a need of taking a large spacing of optical fiber array so that bends will least occur at the connecting portions of optical fibers. This would cause the whole unit to be large sized.
As described above, the disadvantages of the prior art to be solved by the present invention can be summarized as follows:
(1) Because of the difficulty in precisely positioning the optical fiber array on the movable side, it is difficult to attain a precision optical axis alignment between optical fibers; PA1 (2) The optical fiber array is complex in construction and large in weight. Since such a heavy optical fiber array is driven, the actuator is necessarily increased in size, causing the weight to increase, so that the optical switch becomes heavy weight; PA1 (3) Since the optical fiber array is complex in construction and large in size so that the actuator is also large sized, it is difficult to miniature the optical switch; PA1 (4) Because of the large-sized actuator, the power consumption is increased; PA1 (5) Since the optical fiber array of heavy weight is driven against its inertia and the reaction force of the plate spring, the switching speed of switching operation is slow; PA1 (6) Because of the need of high-precision machined parts such as blocks and pin holders as well as the need of a large-sized actuator, the optical switch takes high manufacturing cost; and PA1 (7) Foreign matters stick to the end faces of the optical fibers such that the optical transmission characteristics are deteriorated. PA1 peripheral surfaces of end portions of individual optical fibers constituting a first optical fiber array are in close contact with an optical fiber fitting surface of a base, while the peripheral surfaces of the end portions of the individual optical fibers are in close contact with one another; PA1 peripheral surfaces of end portions of optical fibers on both sides out of the individual optical fibers constituting the first optical fiber array are in close contact with a pair of stopper members, respectively, disposed on both sides of an end portion of the first optical fiber array; PA1 a second optical fiber or optical fiber array is opposed to an end face of the end portion of the first optical fiber array; and that PA1 between projecting portions of the pair of stopper members projected from the end face of the first optical fiber array, peripheral surfaces of end portions of the individual optical fibers constituting the second optical fiber or optical fiber array are in close contact with the optical fiber fitting surface of the base. PA1 holding the optical fiber or optical fiber array so that the end portion thereof is positioned away from the fitting surface of the base; PA1 depressing the optical fiber or optical fiber array toward the fitting surface of the base by using a depressing member, between holding portion and end portion of the optical fiber or optical fiber array, so that the optical fiber or optical fiber array is flexed; PA1 stopping the depressing member in a state that the end portion of the optical fiber or optical fiber array is in close contact with the fitting surface of the base; and PA1 fixing the optical fiber or optical fiber array to the base at at least one place between the holding portion and the end portion of the optical fiber or optical fiber array. PA1 holding the optical fiber array so that the end portions of its individual optical fibers are arrayed in generally parallel with one another and in close contact with the fitting surface of the base; PA1 sandwiching the optical fiber array from both sides between holding portion and end portion of the optical fiber array so that spacings between the optical fibers constituting the optical fiber array are narrowed stepwise, and maintaining the spacings with the end portions of the individual optical fibers kept in close contact with one another; and PA1 bonding the individual optical fibers constituting the optical fiber array, with one another, at at least one place between the holding portion and the end portion of the optical fiber array. PA1 a base having a planar-shaped optical fiber fitting surface; PA1 a holding portion for holding an optical fiber array by sandwiching it against the base; PA1 a first pressing portion which extends from the holding portion and which presses the optical fiber array between the holding portion and an end portion of the optical fiber array so that a peripheral surface of the end portion of the optical fiber array is brought into close contact with the fitting surface of the base; and PA1 a second pressing portion which extends from the holding portion and which presses optical fibers located on both sides in the optical fiber array between the holding portion and the end portion of the optical fiber array so that the peripheral surfaces of the end portion of the optical fiber array are brought into close contact with one another. PA1 a base having a planar-shaped optical fiber fitting surface; PA1 a fixed optical fiber composed of a plurality of optical fibers, peripheral surfaces of end portions of the optical fibers being arrayed in close contact with the fitting surface of the base and in close contact with one another; PA1 a pair of stopper members which are in close contact with peripheral surfaces of end portions of optical fibers located on both sides, respectively, out of the individual optical fibers constituting the fixed optical fiber; PA1 a movable optical fiber composed of optical fiber with the number smaller than that of the fixed optical fiber, peripheral surface of the end portion of the movable optical fiber being in close contact with the fitting surface of the base, end face of end portion of the movable optical fiber being opposed to an end face of an end portion of the fixed optical fiber with a minute spacing; and PA1 drive means for reciprocatingly moving the movable optical fiber along a direction perpendicular to its optical axis within a range restricted by projecting portions of the pair of stopper members that are projected from the end face of the fixed optical fiber. PA1 a holding portion for sandwiching and holding an optical fiber by sandwiching it against the base; PA1 a first pressing portion which extends from the holding portion and which presses the optical fiber between the holding portion and an end portion of the optical fibers so that a peripheral surface of the end portion of the optical fiber is brought into close contact with the fitting surface of the base; and PA1 a second pressing portion which extends from the holding portion and which presses optical fibers located on both sides in the optical fiber, between the holding portion and the end portion of the optical fiber so that peripheral surfaces of the end portion of the optical fiber are brought into close contact with one another. According to this embodiment, when the pressing portion are fitted to the base, the end portion of the optical fiber is put into close contact with the base by the first pressing portion, while their end portions are put into close contact with one another by the second pressing portion. Therefore, the close contact of the optical fibers with the base and the close contact of one optical fiber with another can be easily accomplished, allowing an easy assembly. PA1 a base having a planar-shaped optical fiber fitting surface; PA1 a first optical fiber array composed of a plurality of optical fibers, peripheral surfaces of end portions of the optical fibers being arrayed in close contact with the fitting surface of the base and in close contact with one another; PA1 a second optical fiber array composed of a plurality of optical fibers, end face of end portion of the second optical fiber array being opposed to an end face of an end portion of the first optical fiber array on the fitting surface of the base, peripheral surfaces of end portions of the optical fibers being arrayed in close contact with the fitting surface of the base in close contact with one another; and PA1 a pair of stopper members which are in close contact with peripheral surfaces of end portions of optical fibers located on both sides, out of the individual optical fibers constituting the first optical fiber array and the second optical fiber array.